The present invention relates to a cerclage system for the fixation of injured or fractured bones. The present invention also includes a method of treating injured or fractured bones utilizing a cerclage system. The present invention is particularly useful in the fixation of fractures of the femur and in prophylactic banding of the femur during press fit total hip replacement. The present invention can be used in the treatment of tibia fractures; stabilization of cortical onlay strut grafts; trochanteric reattachments; humerus, patella and ankle fractures. The present invention is also useful in the fixation of "soft" bones such as a sternum after open chest surgery.
In orthopedic surgery where severe breaks of bone have taken place, or in reconstructive procedures on bones, for example reconstructive hip procedures, a permanent cable implant is provided to hold bone portions together. During a total hip replacement, press fit femoral components are inserted into the canal of the femur, resulting in an extremely tight fit in many cases. Seating of the press fit components can sometime result in the induction of large hoop stress in the proximal femur. To counterbalance the induced stress, a cerclage system is provided to apply a counteracting compressive hoop stress. The counteracting stress prevents crack formation and/or propagation.
To apply a sufficient compressive hoop stress, the band portion of the cerclage system is tightened around the bone and clamped in a tensionally stressed state. The band portion of the cerclage is typically provided by a metallic or fabric strip, or preferably a metallic wire or multi-filament cable.
However when the bone heals, the tight fit of the cerclage band around the bone may possibly induce indications of necrosis in the areas of the bone contacted by the cerclage band. Necrosis is caused when there is insufficient blood flow to the bone tissue. To counteract possible necrosis, some cerclage bands may have to be removed after the bone has healed, therefore requiring a later second operative procedure on the patient. Further complicating the second operative procedure is the fact that the bone tends to grow around the band and incorporate it. Therefore removal of the band can be difficult.
Prior attempts have been made to make a cerclage band of a resorable polymeric material. Unfortunately, most resorbable materials do not have sufficient tensile strength to allow them to be optimally utilized as a cerclage band. Therefore most cerclage bands are fabricated from metallic wires or cables. Still another limiting factor is the flexibility of the material which is a critical factor in the operative procedure. Most resorbable materials are not flexible enough for use as cerclage bands.